Currently there is no artificial photosynthetic system that converts carbon dioxide and water with sunlight to a liquid fuel. Such a system needs to be sufficiently efficient for keeping up with the incident flux of solar photons, must be durable, made of Earth abundant materials and with scalable synthetic methods.
Currently the scientific community is investigating the specific problem of efficient catalytic water oxidation, which is a mandatory step of any sunlight to fuel conversion system, by exploring molecular organometallic catalysts or by using electrocatalytic metal oxide deposits in electrochemical cell configurations. The best available molecular catalysts using Earth abundant metals are still far too slow for keeping up with the solar flux, and are unstable. Metal oxide layers of abundant elements deposited onto various metal anodes, especially metal oxides of Co and Mn, are known to catalyze water oxidation typically under harsh (very basic) pH conditions.